The present application relates to force/pressure sensors and, more particularly, to a novel piezoelectric force/pressure sensor capable of measuring static and dynamic force or pressure.
Many force/pressure sensors are well known to the art for use in a multiplicity of diverse applications. The known sensors range from simple spring-actuated devices to elaborate wire and semiconductor strain gages. Each of the sensor types has its own limitations. Spring-actuated sensing devices, for example, are difficult to interface with electronic systems and typically suffer from bearing-wear problems. Strain gages, of wire, semiconductor or other type, generally require careful mounting and elaborate temperature compensation; the output drift of such strain gage sensors often requires manual output zeroing and use in a bridge configuration. Manufacture with the customary bridge configuration is itself relatively expensive. Electronic control technology for such diverse products as home appliances and automobile engines requires a force/pressure sensor which is not only extremely reliable, but also relatively inexpensive to produce. It has been suggested to use piezoelectric transducers for detection of transient or alternating force/pressures, as is utilized for transient sensing of weak sonar echoes and geophysical prospecting over-pressure indications. However, because piezoelectric transducers are of a capacitive nature, such a transducer cannot be directly utilized for sensing static forces or pressures. Accordingly, it is desirable to provide a reliable and relatively inexpensive sensor of the piezoelectric type, which is capable of directly measuring static, as well as dynamic, force/pressure applied to the sensor.